Gas turbine engines, such as those which power aircraft and industrial equipment, employ a compressor to compress air that is drawn into the engine and a turbine to capture energy associated with the combustion of a fuel-air mixture. Oil is used in the engine for purposes of cleaning, cooling, and lubricating components, such as bearings that support one or more shafts of the engine.
Referring to FIG. 2A, an engine oil film damper 200, frequently referred to in the art as a squeeze film damper, uses oil trapped in an annulus 206 defined between a fixed housing 210 and a floating bearing support 214 to damp vibrations in the bearing. The vibrations may be caused by a number of factors, such as an imbalance or a deflection that may exist in the rotational hardware (e.g., rotor) of the engine.
Referring to FIGS. 2A-2B, seals 222a and 222b are used to trap the oil in the annulus 206. The seals 222a and 222b are adjacent to stop clearances 226a and 226b, respectively. There is a substantially constant radial clearance 234 between the housing 210 and a bearing support floor 214a of the bearing support 214, where the bearing support floor 214a is radially inboard/recessed relative to the stop clearances 226a and 226b. As the engine is operated, the oil trapped in the annulus 206 travels around the annulus 206 in a full 360 degree manner.
The oil in the annulus 206 dampens the vibrations that are experienced by providing a resistance to the vibration, or analogously, by providing a restorative force to the bearing support 214 in response to the vibration. The damping may be enhanced by increasing the oil supply pressure, but such an increase in oil supply pressure represents an increase in cost. Accordingly, what is needed are improvements in the design and manufacture of engine bearing dampers that increase the effectiveness/efficiency of the damper without incurring additional penalties/cost in terms of the supporting oil system.